Traditionally, the clock skews, as shown in FIG. 1, are statistically estimated by using a time interval analyzer or a frequency counter. The time interval analyzer measures the time difference of zero-crossing points between the clock signals under test and a reference clock signal, then measures the fluctuations of the time difference through histogram analysis. An example of such a clock skew measurement using a time interval analyzer is described in Jitter Analysis Clock Solutions, by Wavecrest Corporation, 1998.
When evaluating reliability of a microprocessor, for example, it is effective to determine whether the probability of peak-to-peak clock skews in the clocks distributed within the microprocessor exceeds a predetermined value, or to confirm that the generation probability of the peak-to-peak value in the clock skews will not exceed the predetermined value. However, since the generation probability of the peak-to-peak value of the clock skews have never been theoretically analyzed, the traditional method requires an enormous amount of data to estimate the generation probability of the peak-to-peak value of the clock skews, and thus, requiring a large amount of time.